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In this paper, we study the relative anti-canonical divisor $-K_{X/Y}$ of an algebraic fiber space $\phi: X \to Y$, and we reveal relations among positivity conditions of $-K_{X/Y}$, certain flatness of direct image sheaves, and variants of…

Algebraic Geometry · Mathematics 2020-05-12 Sho Ejiri , Masataka Iwai , Shin-ichi Matsumura

Let $(X,B)$ be a projective log canonical pair such that $B$ is a $\Q$-divisor, and that there is a surjective morphism $f\colon X\to Z$ onto a normal variety $Z$ satisfying: $K_X+B\sim_\Q f^*M$ for some $\Q$-divisor $M$, and the augmented…

Algebraic Geometry · Mathematics 2019-02-20 Caucher Birkar , Zhengyu Hu

In this paper we study smooth projective rational surfaces, defined over an algebraically closed field of any characteristic, with pseudo-effective anticanonical divisor. We provide a necessary and sufficient condition in order for any nef…

Algebraic Geometry · Mathematics 2013-03-27 Antonio Laface , Damiano Testa

Let $(X,\Delta)$ be a projective klt pair, and $f:X\to Y$ a fibration to a smooth projective variety $Y$ with strictly nef relative anti-log canonical divisor $-(K_{X/Y}+\Delta)$. We prove that $f$ is a locally constant fibration with…

Algebraic Geometry · Mathematics 2024-08-06 Jie Liu , Wenhao Ou , Juanyong Wang , Xiaokui Yang , Guolei Zhong

Let X be a smooth complex projective variety of dimension d. It is classical that ample line bundles on X satisfy many beautiful geometric, cohomological, and numerical properties that render their behavior particularly tractable. By…

Algebraic Geometry · Mathematics 2007-05-23 Lawrence Ein , Robert Lazarsfeld , Mircea Mustata , Michael Nakamaye , Mihnea Popa

Let $(X,\Delta)$ be a 4-dimensional log variety which is proper over the field of complex numbers and with only divisorial log terminal singularities. The log canonical divisor $K_X+\Delta$ is semi-ample, if it is nef (numerically…

Algebraic Geometry · Mathematics 2007-05-23 Shigetaka Fukuda

In this paper we define certain analogues of the volume of a divisor - called asymptotic cohomological functions - and investigate their behaviour on the Neron--Severi space. We establish that asymptotic cohomological functions are…

Algebraic Geometry · Mathematics 2007-05-23 Alex Kuronya

Let $(X, \Delta)$ be a projective klt three dimensional pair defined over an algebraically closed field characteristic larger than 5. Let $L$ be a nef and big line bundle on $X$ such that $L-K_X-\Delta$ is big and nef. We show that $L$ is…

Algebraic Geometry · Mathematics 2014-03-18 Chenyang Xu

We study the cones of q-ample divisors on smooth complex varieties. In favourable cases, we identify a part where the closure of this cone and the nef cone have the same boundary. This is especially interesting for Fano (or almost Fano)…

Algebraic Geometry · Mathematics 2016-02-17 Robert Laterveer

Under some conditions on the deformation type, which we expect to be satisfied for arbitrary irreducible symplectic varieties, we describe which big and nef line bundles on irreducible symplectic varieties have base divisors. In particular,…

Algebraic Geometry · Mathematics 2018-07-16 Ulrike Riess

In this paper we explore the connection between asymptotic base loci and Newton-Okounkov bodies associated to infinitesimal flags. Analogously to the surface case, we obtain complete characterizations of augmented and restricted base loci.…

Algebraic Geometry · Mathematics 2015-07-16 Alex Küronya , Victor Lozovanu

In this paper, we prove the ampleness conjecture and Serrano's conjecture for strictly nef divisors on K-trivial fourfolds. Specifically, we show that any strictly nef divisors on projective fourfolds with trivial canonical bundle and…

Algebraic Geometry · Mathematics 2024-01-11 Haidong Liu , Shin-ichi Matsumura

We construct log resolutions of pairs on the blow-up of the projective space in an arbitrary number of general points and we discuss the semi-ampleness of the strict transforms. As an application we prove that the abundance conjecture holds…

Algebraic Geometry · Mathematics 2019-04-08 Olivia Dumitrescu , Elisa Postinghel

Let X be a projective irreducible symplectic manifold and L a non trivial nef divisor on X. Assume that the nef dimension of L is strictly less than the dimension of X. We prove that L is semiample

Algebraic Geometry · Mathematics 2007-05-23 Daisuke Matsushita

Let F be the quotient of an analytic function with a product of linear functions. Working in the framework of analytic combinatorics in several variables, we compute asymptotic formulae for the Taylor coefficients of F using multivariate…

Combinatorics · Mathematics 2022-07-26 Yuliy Baryshnikov , Stephen Melczer , Robin Pemantle

We generalize Nakamaye's description, via intersection theory, of the augmented base locus of a big and nef divisor on a normal pair with log-canonical singularities or, more generally, on a normal variety with non-lc locus of dimension at…

Algebraic Geometry · Mathematics 2014-12-24 Salvatore Cacciola , Angelo Felice Lopez

We prove that if $(X, B+\mathbf{M})$ is a generalized klt pair with $K_X+B+\mathbf{M}_X$ nef and abundant, then $K_X+B+\mathbf{M}_X$ is semiample. More generally, we prove a generalized basepoint free theorem for generalized klt pairs.

Algebraic Geometry · Mathematics 2023-04-18 Priyankur Chaudhuri

In this article we prove a finiteness result on the number of log minimal models for $3$-folds in char $p>5$. We then use this result to prove a version of Batyrev's conjecture on the structure of nef cone of curves on $3$-folds in…

Algebraic Geometry · Mathematics 2018-09-17 Omprokash Das

Let $L$ be a nef and big line bundle on a scheme $X$. It is well known that if $X$ is a projective over a field then the augmented base locus and the exceptional base locus agree. This result is extended to projective schemes over arbitrary…

Algebraic Geometry · Mathematics 2023-02-07 Liam Stigant

We conduct the multifractal analysis of the level sets of the asymptotic behavior of almost additive continuous potentials $(\phi_n)_{n=1}^\infty$ on a topologically mixing subshift of finite type $X$ endowed itself with a metric associated…

Dynamical Systems · Mathematics 2011-04-11 Julien Barral , Yan-Hui Qu